U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF ENTOMOLOGY— BULLETIN No. 56. 

O B L - O. HOWARD, Entomologist. 

945 

THE BLACK HILLS BEETLE, 



WITH 



FURTHER NOTES ON ITS DISTRIBUTION, LIFE HISTORY, 
AND METHODS OF CONTROL 



PREPARED UNDER THE DIRECTION OF THE ENToMOLotj 1ST. 
BY 

A. D. HOPKINS, Ph. D., 
In Cftdrge of Porest Insect Investigations. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE, 

1905. 




Qass XV J-'- , 
Book _.: 



U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF ENTOMOLOGY— BULLETIN No. 56. 

L. O. HOWARD, Entomologist. 



ff-lT 



' i- 



THE BLACK HILLS BEETLE, 



WITH 



FURTHER NOTES ON ITS DISTRIBUTION, LIFE HISTORY, 
AND METHODS OF CONTROL. 



PREPARED UNDER THE DIRECTION OF THE ENTOMOLOGIST. 
^ / BY 

AfDy ^OPKINS, Ph. D., 

In Charge of Forest Insect Investigations. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE, 

1 9 5 . 



C T^ 



£>? 



^ 






LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 

Bureau of Entomology, 

Washington, D. C, November 14, 190-5. 
Sir: I transmit herewith the manuscript of the report of Dr. 
A. D. Hopkins, of tins Bureau, on an investigation of the Black Hills 
beetle, with especial reference to its occurrence in the Pikes Peak 
Forest Reserve and in the vicinity of Colorado Springs and Palmer 
Lake. This investigation was made at the request of the Bureau 
of Forestry, and I recommend the publication of the report, which 
brings the information concerning this species up to date, as Bulletin 
56 of this Bureau. The figures and plates are necessary for the 
illustration of the text. 
Respectfully, 

L. O. Howard, 
Entomologist and Chief of Bureau. 
Hon. James Wilson, 

Secretary of Agriculture. 



CONTENTS. 



Page. 

Introductory 5 

Historical references 5 

Report on forest insect investigation in the Pikes Peak Forest Reserve. 8 

Objects 8 

Explorations 9 

Summary of results, conclusions, and recommendations 9 

The Black Hills beetle 10 

Characters of the beetle 11 

Characters of the gallery 11 

Characters of the infested trees 13 

Life history 15 

Natural and artificial influences 16 

Drought and cold 16 

Lightning 16 

Storms 16 

Fire 16 

Commercial cutting 17 

Summer cutting in patches 17 

Trap trees 17 

Natural enemies 18 

Insects 18 

Birds 18 

Diseases of insects 18 

Secondary enemies of the trees, and neutral insects 18 

Methods of control .« 19 

Application of the method in the Black Hills 19 

Application of the method in Colorado 20 

Further recommendations relating to the control of the beetle 21 

Note 22 

Index 23 

3 



LLUSTRATIONS. 



Plate I. Work of the Black Hills beetle. Fig. 1. — Primary galleries and larval 
mines in inner bark. Fig. 2. — Marks of primary galleries on surface 

of scoring chip 12 

II. Work of the Black Hills beetle. Fig. 1. — Marks of primary galleries on 
surface of wood when bark is removed. Fig. 2. — Freshly attacked 
tree, showing pitch tubes; adjoining tree not attacked 14 

TEXT FIGURES. 

Fig. 1. The Black Hills beetle: adult 11 

2. Work of the Black Hills beetle : primary galleries and larval mines in inner 

surface of living bark 12 

3. Work of the Black Hills beetle, in inner bark of dead tree 13 

4. Work of the Black Hills beetle: pitch tubes on surface of bark 14 

5. The Black Hills beetle: larva 15 

6. The Black Hills beetle : pupa 15 

4 



THE BLACK HILLS BEETLE. 

(Dendroctonus ponderosce a Hopk.) 



INTRODUCTORY. 

The object of this bulletin is to give additional information on 
the distribution, life history, habits, and methods for the control 
of the Black Hills beetle, based on further investigations by the 
writer and his field assistants, and information through correspond- 
ence with forest officials and others. 

It is now known that this beetle occurs in the eastern sections of 
the Rocky Mountain region from the Black Hills of South Dakota 
to northern New Mexico; and there is evidence that its distribution 
extends westward into Utah and northern Arizona. 

It attacks and kills the western yellow or bull pine (Pinus pon- 
derosa) and the white spruce (Picea canadensis) in the Black Hills 
of South Dakota; and the western yellow or bull pine, the limber 
pine (Pinus flexilis), and the Engelmann spruce (Picea engelmanni) 
in the Pikes Peak region. 

Wherever this insect is found in abnormal numbers its depreda- 
tions on living timber are more or less extensive. It has killed 
between 700,000,000 and 1,000,000,000 feet of timber in the Black 
Hills Forest Reserve, and is also demonstrating its destructive 
powers in central Colorado and New Mexico. 

The method for its control recommended by the writer and 
adopted in the Black Hills and Pikes Peak region has been suffi- 
ciently tested to show that it is both practicable and effective, and 
that, under proper management, a forest can be protected at a 
moderate expenditure, or almost without cost where there is a 
market for the timber. 

HISTORICAL REFERENCES. 

Probably the earliest published information on the destructive 
work of this insect is that by Prof. H. S. Graves, 6 in which he refers 
to the dying pine timber in the Black Hills of South Dakota. He 
stated that the patches of dying and dead timber are usually rec- 
tangular in shape, following the tops of the divide or ridges and 
running lengthwise up and down the slope, and that this injury was 
probably caused by bark-boring insects of a species of Scolytidae. 

a Family Scolytidas. b Ninth Rept. U. S. Geol. Surv., Pt. V, p. 87, 1897-98. 

5 



6 THE BLACK HILLS BEETLE. 

Specimens of the bark-boring insects found attacking the living 
trees in the area mentioned by Professor Graves were sent to the 
Department of Agriculture in August, 1898, by Mr. William M. Pratt, 
from Piedmont, S. Dak., and by Mr. H. E. Dewey, from Lead, S. Dak., 
and more specimens were sent in by Mr. Dewey in August, 1899. 
These were at first identified as Dendroctonus rufipennis Kirby, and 
as D. terebrans Oliv.; but in 1900 they were examined by the writer 
and were found to represent an undescribed species of Dendroctonus. 
Specimens of the same insect were also found in the collections of the 
American Entomological Society, at Philadelphia, and in the United 
States National Museum, labeled South Dakota, Utah, and Colorado, 
the latter from Pikes Peak, July 10, 1900. 

In September, 1901, upon the request of Mr. Gifford Pinchot, 
Chief of the Bureau of Forestry, and under the direction of Dr. 
L. O. Howard, Chief of the Division of Entomology, an investiga- 
tion of the trouble affecting the timber in the Black Hills Forest 
Reserve was made by the writer; and on October 23, 1901, a type- 
written report was submitted to Doctor Howard and Mr. Pinchot 
which, with additional data and illustrations, was transmitted for 
publication in January, 1902, and was issued in that year as Bulletin 
No. 32, new series, of the Division of Entomology. In this bulletin 
the new species found to be the primary cause of the death of the 
timber was described under the name of Dendroctonus ponderosse, 
and certain facts in its habits and life history were presented, 
together with recommendations based thereon, for felling and barking 
the infested trees at a time of the year when the mere removal of the bark 
from the main trunk, without burning, would be sufficient to kill the 
broods. 

In July, 1902, Mr. John P. Brown, secretary of the International 
Society of Arboriculture, issued a "Special Rocky Mountain Bulletin 
on the Destructive Beetles of Pinus ponder 'osa," in which reference is 
made to the destruction of pine timber in the Black Hills of South 
Dakota and in Colorado by two beetles, which he designates as the 
"large destructive barkbeetle" and the "small destructive bark- 
beetle," but he omitted their scientific or "technical names. There- 
fore it is not known to what particular species he referred, or whether 
or not he had two or more species confused. It is evident, however, 
that the depredations in the Black Hills were caused by D. ponderosse, 
previously described. 

Mr. Brown recommended the remedy of felling and barking the 
trees and burning the bark with the tops ; but his main argument was 
for the protection of insectivorous birds. 

In 1902 Mr. J. L. Webb, special field agent in forest insect investi- 
gations, assigned from the Bureau of Forestry, and working under 
instructions from the writer, spent five months (May 28-October 30) 



THE BLACK HILLS BEETLE. 7 

in the Black Hills Reserve, studying the life history and habits of the 
beetle. He also conducted extensive trap-tree experiments, in which 
over two hundred matured healthy trees were girdled or felled to 
determine their attractive influence on the Black Hills beetle and 
other forest-tree insects. In August, 1902, and June, 1903, the 
writer visited the reserve and made special studies of the beetle and 
of the trap-tree experiments. In October and November, 1902, and 
November, 1904, Field Assistant H. E. Burke visited the reserve for 
the same purpose, and Forest Ranger W. G. Courtney made records 
of observations on the trap trees from June to October, 1903. 

August 12, 1902, Prof. C. P. Gillette sent specimens of a barkbeetle 
from Bailey, Colo., with a statement that he had found it in dying 
pine trees. Tins proved to be the Black Hills beetle, D. ponderosse, 
and was the first authentic record of its work in Colorado. 

During a special investigation in May, 1903, the writer found the 
same species in northwestern New Mexico, in the vicinity of Vermejo, 
where it was attacking and killing the matured pine timber over a 
large area. Here the method of cutting and barking the infested 
trees was recommended. 

In December, 1904, specimens of the beetle were sent by Mr. P. P. 
Blass, with a statement that a large amount of timber was dying in 
the vicinity of Palmer Lake. In reply, Mr. Blass's attention was 
called to the dangerous character of this enemy of pine trees, and 
published data on the subject, supplemented by written instructions 
for the cutting and barking of infested trees, were sent him. Upon 
the suggestion of Mr. Blass, on February 15, 1905, a set of bulletins 
and written instructions were also sent to the town board of Palmer 
Lake. This resulted in the cutting and barking of a large number 
of infested trees by different people in that vicinity. Upon infor- 
mation from the clerk of the town board of Palmer Lake that the 
timber was dying in the forest reserve, adjoining the town property, 
information was conveyed by the writer to the Forest Service, to- 
gether with copies of recommendations for the cutting and barking 
of infested timber ; also stating that upon receipt of information from 
the supervisor as to the character and extent of the trouble in the 
reserve, the Bureau of Entomology would take the matter up with 
them and, if necessary, send a man into the field to make special 
investigations. Later a report of May 11, 1905, addressed to the 
Forest Service by Supervisor Clarke, was referred to the writer on 
May 17. In reply to this, more detailed instructions were sent to 
Supervisor Clarke, for the identification of the trees which should be 
cut, with the statement that it would be more desirable for the 
Bureau to make an investigation in the fall. 

In a letter dated July 14, 1905, Prof. C. P. Gillette, State ento- 
mologist of Colorado, stated that during a visit to Palmer Lake he 



8 THE BLACK HILLS BEETLE. 

noted that a large amount of timber was dying in that vicinity. 
The specimens sent to the Bureau of Entomology with his letter 
proved to be the Black Hills species, thus leaving no doubt regarding 
the primary enemy and the great danger of an invasion which might 
soon extend beyond control unless active measures were adopted. 

In the meantime, General Palmer, certain members of the faculty 
of the Colorado College, and others interested in the protection of the 
forests in the vicinity of Colorado Springs had inaugurated an active 
campaign to control the ravages of the beetle, in which the services of 
Prof. Lawrence Bruner, of the University of Nebraska, were secured 
to make investigations and give instructions in felling and barking 
the timber. Two reports were submitted by Professor Bruner to 
General Palmer, one dated August 2, the other September 19. These 
reports, together with correspondence and other data, were published 
in Arboriculture for October, 1905, pages 205-212. 

Under Professor Bruner' s direction between 600 and 800 trees 
on private lands in the vicinity of Glen Eyrie, Colorado Springs, and 
adjoining the reserve were felled during August, September, and 
October, and the bark removed and burned with the tops, to kill the 
insects with which they were infested. 

On September 16 a full report of the results of explorations by 
the forest rangers in the Pikes Peak Forest Reserve was submitted to 
the Chief of the Forest Service by Supervisor Clarke. This included 
specified descriptions of ranges and sections containing infested 
timber which General Palmer had requested permission to cut and 
bark at his own expense, for the further protection of the surrounding 
public and private forests. Copies of these typewritten reports 
and statements were submitted by the Acting Forester for consid- 
eration, and upon consultation with Mr. Gifford Pinchot, Forester, 
and Mr. Overton W. Price, Associate Forester, it was decided that 
the writer should proceed at once to make the necessary investiga- 
tion on which to base recommendations for the consideration of 
forest officials and others, in further efforts to control the destruc- 
tive insects in and around the Pikes Peak Reserve. 

This investigation was made October 5 to 13, 1905, and the fol- 
lowing report submitted : 

REPORT ON FOREST INSECT INVESTIGATIONS IN THE PIKES 
PEAK FOREST RESERVE. 

OBJECTS. 

The object of this special trip was to investigate the character and 
extent of depredations by the pine-destroying beetle of the Black 
Hills (Dendroctonus ponderosse Hopk.) in the pine forests of the Pikes 
Peak Forest Reserve, in the vicinity of Colorado Springs and Palmer 



THE BLACK HILLS BEETLE. 9 

Lake and at such other points as might be deemed necessary; to give 
instructions to the forest officials and others in carrying out our rec- 
ommendations for the control of this and other insects directly 
associated with the dying timber, and to determine for the Forest 
Service the approximate extent of necessary cutting of timber on the 
reserve to protect the remaining living timber in the vicinity of Col- 
orado Springs and adjoining private estates, as proposed by Gen. 
William J. Palmer. 

EXPLORATIONS. 

Beginning on the morning of October 5 explorations were made as 
follows: Glen Eyrie trail on mountain northward, returning via 
Douglass Canyon; October 6, from Glen Eyrie by way of Colorado 
City, Bear Creek Canyon, High Line road, to Bruin Inn, returning by 
way of North Cheyenne Canyon, Colorado Springs, and Palmer Park; 
October 7, from Glen Eyrie by way of Manitou, over Crystal Park 
trail to Crystal Park, returning by the Bear Creek trail, Bear Creek 
Canyon, and Colorado Springs; October 8, from Glen Eyrie, by way 
of Blair Athol, Pike View, Pope Ranch, and Palmer Park; Octo- 
ber 9, from Colorado Springs by way of Colorado Springs and Cripple 
Creek Railway to Clyde, thence by wagon to an altitude of about 
10,000 feet, returning by same route to Colorado Springs; October 

10, from Colorado Springs by way of the Colorado Midland Rail- 
road to Woodland Park, thence by wagon to Manitou Park; October 

11, by saddle from Manitou Park east to Palmer Lake, thence by 
wagon southeast by way of Husted to Woodland Ranch; October 

12, in the Colorado pinery on the Arkansas and Platte divide; Octo- 
ber 13, in the Colorado pinery, returning by way of Colorado Springs 
to Glen Eyrie. 

Additional explorations were made on the 12th and 13th by Mr. 
Edmonston, under my instructions, in the vicinity of Palmer Lake. 

During all but one of these trips I was accompanied by Mr. W. D. 
Edmonston, head ranger of the Pikes Peak Forest Reserve, who was 
designated by Forest Supervisor Clarke as the proper official to 
receive instructions in the identification of the infested trees to be 
felled and barked to kill the principal insect enemies. I was also 
accompanied on a number of the trips by General Palmer's foreman, 
who received similar instructions. Supervisor Clarke accompanied 
us on two trips, General Palmer on three, and Forest Assistant 
Clement on two. 

SUMMARY OF RESULTS, CONCLUSIONS AND RECOMMENDATIONS. 

(1) The depredations by the Black Hills beetle (Dendroctonus 
ponderosx Hopk.) within the area examined are by no means as 
extensive as we were led to believe from the reports and correspond- 
ence. 

12405— No. 56—06 2 



10 THE BLACK HILLS BEETLE. 

(2) The principal areas of recent damage by this beetle in the 
reserve and on private lands are in the vicinity of Cascade and 
Palmer Lake; but evidence of old and new work was observed to be 
more or less frequent in all sections visited. 

(3) The evidence found on old, dead, standing, and felled trees of 
the work of the Black Hills beetle on pine, the spruce-destroying 
beetle (Dendroctonus piceaperda Hopk.) on Engelmann spruce, and 
the Douglas spruce Dendroctonus (D. pseudotsugse Hopk. MSS.) on 
Douglas spruce indicate that all of these species have been present and 
destructive to living timber in this region for at least fifty years. 
The number and distribution of such old beetle-marked trees indi- 
cate that very extensive depredations have been wrought by them 
in the Pikes Peak region within the past century; and present 
conditions also indicate that a large per cent of the vast destruction 
of timber, heretofore attributed to fire, was primarily due to the 
work of these insects. 

(4) The three species of bark beetles above mentioned are without 
doubt the most important insect enemies of conifer forests in the 
central Rocky Mountain region; hence they are a constant menace 
to the remaining living timber in and around the reserves of central 
Colorado. 

While at present the spruce-destroying beetle appears to be rare, 
and the Douglas spruce and Black Hills beetles are not common 
enough to cause extensive depredations, it is plain, from what is 
known of the destructive powers of these insects, that if neglected 
and if specially favorable conditions for their multiplication should 
prevail for two or more years in succession they could easily destroy 
all of the timber of commercial size and a large per cent of the 
reproduction. 

THE BLACK HILLS BEETLE. 

The Black Hills beetle (D. ponderosse) is at present the most com- 
mon and destructive enemy of the living pine timber in and around 
the Pikes Peak Reserve; therefore it should receive primary con- 
sideration. 

The best success in any efforts by forest officials or private owners 
of forests to control this beetle will depend on a sufficient knowledge 
of the species, its habits, life history, and the influences which are 
favorable or unfavorable for its increase and destructive invasions. 

Insufficient knowledge on these points results in the confusion of 
the primary and secondary enemies of the tree, unnecessary expendi- 
ture of time and money, by felling and barking trees at the wrong 
time of the year, or after the broods of the primary enemy have 
emerged, the felling of living trees which would have recovered, 
and the unnecessary destruction of beneficial insects and insect dis- 
eases by burning the bark. 



THE BLACK HILLS BEETLE. 



11 



The following description of distinctive characters of the beetle, 
its work, habits, life history, etc., is based on the results of our 
studies of the species in the field and laboratory, brought up to date, 
regardless of what has been previously published or given out in 
correspondence. 

CHARACTERS OF THE BEETLE (FIG. 1). 

The distinctive characters of the Black Hills beetle are its length, 
which is from one-sixth to one-fourth of an inch; its stout form, 
with broad head and pro thorax; its black color, and the rounded 
or convex rear end of the body (declivity of the elytra), which is 
without conspicuous long hairs. The allied species, which may be 
mistaken for it, are distinguished as follows: The large red turpen- 
tine beetle (Dendroctonus valens Lee.) is much larger, is dark reddish 
in color, never black, and forms large 
masses of pitch at or toward the base of 
living and dying pine trees and stumps. 
The Colorado Dendroctonus (D. approxi- 
mate Dietz) is black, with broad head, 
but the body is more elongate, the front 
of the head is grooved, and the declivity 
of the elytra has long, stiff hairs; it lives 
in the bark of pine, but makes a winding, 
sometimes branched, gallery. The spruce- 
destroying beetle (Dendroctonus piceaperda 
Hopk.) is reddish brown to black, but with 
much narrower head, with long hairs on the 
declivity of the elytra, and is always found 
in spruce. The Douglas spruce beetle 
(Dendroctonus pseudotsugse n. sp.) is dark red or brown, and always 
breeds in Douglas spruce and western larch. The species which most 
closely resembles the Black Hills beetle is the mountain-pine beetle 
(Dendroctonus monticola Hopk.), which is only distinguished in the 
adult stage by the smaller size, slightly less stout form, less dis- 
tinctly roughened elytra, and more obscured rows of punctures on 
the sides of the elytra, the latter being the most important char- 
acter for its distinction. 




Fig. 1.— The Black Hills beetle: a, 
adult, enlarged; 6, same, natural 
size. (Author's illustration.) 



CHARACTERS OF THE GALLERY (FIGS. 2 AND 3 AND PL. i). 

The primary gallery excavated in the bark by the Black Hills 
beetle is distinguished from that of any other species as yet known 
to live in the pine of the Black Hills or Colorado by the slight curve 
at the entrance end and the almost straight course with the grain 
through the inner layers of bark, and grooving the surface of the 
wood. There is only one pine-infesting species with which tins form 



12 



THE BLACK HILLS BEETLE. 



of gallery can be confused, namely, the mountain pine beetle, which 
has not as yet been found in the same region. If it should occur, 
however, the galleries may be distinguished by the smaller size, more 




Pig. 2.-Work of the Black Hills beetle {Dendroctonus ponderosx Hopk.). Primary galleries and 
larval mines in inner surface of living bark: a, entrance and basal chamber; b, ventilating holes in 
roof of gallery; c, termination. The larval mines radiate from the primary galleries. About one- 
half natural size. (Author's illustration.) 

crooked and slightly winding course, and by the fact that they are 
more commonly met with in the silver pine, limber pine, and lodge- 
pole pine. Whenever the Black Hills species is found in spruce the 



Bui. 56, Bureau of Entomology, U. 5. Dept. of Agriculture. 



Plate 




THE BLACK HILLS BEETLE. 



13 



gallery is distinguished from that of the spruce-destroying beetle by 
its slender form and more evenly distributed side or brood mines. 

CHARACTERS OF THE INFESTED TREES (FIG. 4 AND PL. Il) . 

Trees attacked by the Black Hills beetle between July and October 
will be indicated by the presence of pitch tubes, or sawdust borings, 
and upon removal of the bark the young broods will be found mining 
through the inner living layers, or the bark will be entirely killed on 
the main trunk; but the foliage will remain green, or will be but 
faintly faded until 
May and June of 
the following year, 
when the leaves on 
the lower branches 
will turn yellow and 
die. This condition 
will rapidly extend 
to the topmost 
leaves, so that by 
the time the broods 
of maturing beetles 
are ready to emerge 
the foliage is yel- 
lowish red to light 
reddish brown in 
color. This is the 
stage of death called 
"sorrel tops." 
Later in the sum- 
mer and during the 
following winter, 
after all living ex- 
amples ot tne beetle FlG 3 _ Work of the Black Hills beetle in irmer bark of dead tree: 

have emerged, the a, primary galleries ; b, larval mines; c, pupal chambers ; d, exit holes. 
folincrp iq dark red- Reduced about one-half. (Author's illustration.) 

dish brown, called "red tops." This condition prevails during the 
second summer after attack; but by the third summer all, or nearly 
all, of the leaves have fallen, which gives the tops of the dead trees a 
blackish appearance, called "black tops." 

Beginning with freshly attacked trees during the first summer, 
they are distinguished by the exudation of fresh whitish or reddish 
pitch forming small masses or tubes on the bark of the main trunk 
or by the presence of fresh reddish sawdust-like borings lodged in 
the loose bark and around the base of the tree. 







14 



THE BLACK HILLS BEETLE. 



Trees infested with partially to fully developed broods from the 
latter part of August to the first of November, and during the period 
of inactivity, are distinguished by numerous pitch tubes over and 
entirely around the middle portion of the trunk and extending more 

or less toward the base and 
top. The age of the pitch 
tubes is indicated by their 
relatively moist or dry con- 
dition. A successful or vital 
infestation will be shown by 
the large number of pitch 
tubes surrounding the entire 
trunk, and also by their red- 
dish color and general ap- 
pearance. An unsuccessful 
attack — from which the tree 
will recover — is indicated 
after the first of November 
by a small number of smooth 
whitish pitch masses scat- 
tered about over the trunk, 
confined to or toward the 
base; their absence on the 
middle to upper portion of 
the trunk or, if present there, 
their failure to completely 
surround it. 

Positive evidence as to 
whether or not a green- 
topped, pitch-marked tree is 
infested by living broods is 
determined only by cutting 
into the bark at different 
places, 4 to 8 feet from the 
base. This test should be 
made during the inactive 
period, when trees are being 
marked for cutting. 

Soon after activity begins 
in the spring, infested trees 
are distinguished by a pale appearance of the foliage, followed by a 
yellow or reddish brown color, as if killed by fire. 

Dead trees which have been killed by the Black Hills beetle but 
are no longer infested by living broods are distinguished during the 
summer, fall, and winter by the old dry pitch tubes on the bark and 
the dark reddish brown or "black-topped" condition. The only 




Fig. 4.— Work of the Black Hills beetle: a, pitch tubes on 
surface of bark, much reduced; b, same, two-thirds 
natural size. (Author's illustration.) 



Bui. 56, Bureau of Entomology, U. S. Dept. of Agriculture 



Plate II. 



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THE BLACK HILLS BEETLE 



15 




exception to this is when the top portion of the tree or one side of 
the trunk is killed the first year and a brood develops in the remain- 
ing living bark the next year. This sometimes occurs, but is never 
common enough to require special notice. Its occasional occurrence, 
however, explains why broods of the beetle are sometimes found in 
trees which appear to have been dead for two or three years. 

LIFE HISTORY. 

The insect passes the winter, or inactive period, in all stages — as 
larva?, pupae, and adults — beneath the bark of trees attacked by 
the parent beetles during the previous summer 
and fall. Activity begins in the spring as soon as 
sufficient warm weather prevails, when the broods 
continue to develop and mature, but remain in the 
bark until about the middle of July (Black Hills, 
latitude 44°, altitude 7,000 feet), probably later 
northward and at higher altitudes, and earlier 
southward and at lower altitudes. When the 
adults (fig. 1) begin to emerge from the bark of the 
trees in which they had developed from eggs depos- 
ited the previous year, they usually fly in swarms, 
and attack the living trees, in which they excavate 
galleries through the inner layer of bark and groove FlG 5 ._L a rva 
the surface of the wood. Along the sides of these 
primary galleries excavated by the beetle, eggs 

are deposited for the next generation, which, as be- 
fore, hatch into grubs or larva? (fig. 5) , which mine at 
right angles to the primary galleries through the inner 
bark, on which they feed. This feeding. and growing 
stage continues during the first summer, some of the 
individuals completing their development before fall, 
so that all stages, including the pupa? (fig. 6) , may be 
found during the fall in the trees attacked in July. 
These with the younger broods remain dormant dur- 
ing the winter and complete their development the 
following spring in time to emerge in their regular 
course during the following summer. 

The period of flight of the beetles and of then attack 
(Author's nius- on u^ing trees, as well as the egg-depositing period, is 
about seventy-five days, beginning about the middle 
of July and ending about the first of October. The exact time of 
the beginning and ending of this period in a given locality depends 
upon the latitude, altitude, and local conditions. The normal 
period of development of a brood from the time the living tree is 
attacked and the eggs deposited until the adults emerge from the 



Black Hills beetle. 

(Author's illustration.) 




Fig 6— Pupa of the 

Black Hills beetle. 



16 THE BLACK HILLS BEETLE. 

dying or dead trees is about three hundred and fort}^ days. The 
period of activity — the feeding, growing, and maturing stages — of 
all broods of a single generation during the fust summer is about 
ninety days — July 15 to October 15 — and about one hundred and 
fifty days from the time activity begins the following spring — early 
in May — until the last individual has developed and emerged — early 
in October. Thus there is a total active period of about two hundred 
and forty days. The period of inactivity — from about October 15 
to early in May — is about one hundred and ninety-five days, making 
the total period of infestation of all broods of a single generation 
about four hundred and thirty-five days. This, of course, provides 
for an overlapping of the last broods of one generation and the first 
broods of the next, during July, August, and September. 

NATURAL AND ARTIFICIAL INFLUENCES. 
DROUGHT AND COLD. 

It has been a common belief that the dying of the timber is caused 
by drought, but it is now clearly demonstrated that wherever the 
Black Hills beetle is abundant it kills the healthiest trees under all 
conditions of dry and wet seasons, moist or dry soils, north or south 
slopes, ridges, etc. It has also been demonstrated that it can with- 
stand a temperature of 30° to 40° F., or more, below zero. 

LIGHTNING. 

It has been found that trees struck by lightning, or at least those 
struck in summer, are usually attacked by this beetle, and that 
such trees serve to perpetuate the species at times when it does 
not occur in sufficient numbers to kill trees on its own account. 
Such trees also serve to support the natural enemies of the beetle, 
including insects, diseases, and birds. 

STORMS. 

Storm-felled living trees also serve as emergency breeding places, 
and if the storm occurs at the proper time in the year to make the 
conditions especially attractive to the beetles when they are flying, 
they may be attracted for long distances. This concentration of 
scattering forces breeding in felled timber may form the nucleus for 
a destructive invasion. This has been demonstrated from time to 
time in Europe, where even secondary enemies of the genus Tomicus 
have been thus enabled to multiply in such great numbers as to 
attack and kill living forests. 

FIRE. 

Our observations so far have failed to reveal much evidence that 
this species will breed in trees injured or killed by fire in sufficient 



THE BLACK HILLS BEETLE. 17 

numbers to materially aid their increase. Indeed, newly fire- 
scorched trees observed near a sawmill in the Manitou Park section 
showed no trace of the presence or work of this beetle, although the 
trees were being attacked by several species of secondary enemies, 
including the true turpentine beetle {Dendro clonus valens Lee). On 
the other hand, an extensive forest fire may contribute to the destruc- 
t ion of the Black Hills beetle by burning the dead bark from the liv- 
ing and dying infested trees, which may explain the evident sudden 
endings of old invasions. 

COMMERCIAL CUTTING. 

The cutting of living trees for commercial purposes has appar- 
ently little or no influence on the multiplication of the beetle. While 
it will breed in freshly cut logs from living trees, our experiments 
show that it prefers to attack standing timber. Then, again, any 
operations which involve the removal of the bark from the logs for 
ties, mining timbers, etc., will destroy any broods which may be 
therein. If cut into cord wood, the bark will soon become too dry 
for the insect to live in. Slabs from freshly cut logs may favor its 
development in small numbers, but usually the conditions in such 
material are not favorable. Neither do the green stumps, so far 
as we have observed, offer sufficiently attractive breeding places 
for this beetle to warrant the barking of such stumps. Nothing in the 
slash will offer favorable breeding places, except the tops of the main 
trunk, and this is seldom sufficient to warrant any special treatment. 

SUMMER CUTTING IN PATCHES. 

The cutting of living infested trees and of healthy trees in local 
commercial cuttings is objectionable from the fact that we have 
found that when a few living trees are felled in the midst of a forest 
where this beetle is present in numbers it will be attracted by the 
odor and will attack the surrounding standing timber. Therefore 
such local summer cuttings should be avoided. 

TRAP TREES. 

This is a method of combating bark beetles in which trees are 
girdled or felled to attract the insects to them, after which the broods 
are destroyed by stripping off the bark or burning the entire tree. 

Trap-tree experiments were conducted by Mr. J. L. Webb, under 
the writer's instructions, in the Black Hills Reserve in 1902, in which 
trees were felled, hack girdled, girdled to the heartwood, belt girdled, 
and hacked and peeled at intervals of five or six days between June 
2 and October 30. The result of this experiment showed conclu- 
sively that no method of preparing the trap trees was of sufficient 



18 THE BLACK HILLS BEETLE. 

value in its attractive influence on the Black Hills beetle to warrant 
its adoption in efforts to control this insect. While many of the 
trap trees were attacked, the percentage and density of the infesta- 
tion were no greater than in near-by or distant healthy trees. On 
the other hand, it was shown conclusively that the felled trap trees 
were especially attractive to one of the most important secondary 
enemies, namely, the Oregon Tomicus (Tomicus oregoni Eichh.). 

NATURAL. ENEMIES. 
INSECTS. 

While a number of insect enemies of the Black Hills beetle have 
been found during our investigations, they appear to have little effect 
when the timber is dying over large areas, but under normal condi- 
tions of scattering infested trees they seem to render valuable serv- 
ice in preventing the rapid multiplication of the destructive beetle. 

BIRDS. 

The work of woodpeckers is frequently seen on infested trees, but, 
like the beneficial insects, they do their greatest service, perhaps, 
in helping to preserve the normal balance in the struggle of the trees 
against insects and of the insects against their own enemies. 

DISEASES OF INSECTS. 

Evidence was frequently found of the destruction of part or all of 
the broods in an infested tree by fungous diseases, but to what 
extent this factor affects the decrease of the beetle has not been 
determined. 

SECONDARY ENEMIES OF THE TREES, AND NEUTRAL INSECTS. 

Insects which attack only weakened, dying, or dead trees, and 
those associated with a destructive or primary enemy are called sec- 
ondary enemies. Insects which simply live under the bark or feed 
on fungi, dead wood, and bark are in no manner responsible for 
injury to the tree. Thus they are either neutral insects, scavengers, 
or guests. 

There are so many of all of these classes of insects associated witli 
the Black Hills beetle in trees killed by it that it would require too 
much space to discuss them in this connection; but it seems neces- 
sary to say that the greatest care should be taken to avoid confusing 
some of the species of secondary enemies with the primary one, and 
that when there is the slightest doubt specimens should be sent to 
this Bureau for identification. 



THE BLACK HILLS BEETLE. 19 

METHODS OF CONTROL. 

The results of our investigations to date suggest but slight changes 
in our recommendations in 1901 and 1902, published in Bulletin 32 
(pp. 21, 22), as follows: 

It appears that the pine-destroying beetle of the Black Hills, like its eastern relatives, 
depends on the trees killed by it for the augmentation of its numbers and the perpetuation 
of its power of killing more trees. Therefore it is only necessary that the attacking force be 
reduced to a point where it can no longer overcome the vital resistance of the trees on which 
it concentrates its attack in order to successfully defeat it. 

The fact that the attacking force of the enemy is already weakened from natural agencies 
suggests that they can be reduced by artificial means below their power of killing more trees 
next season, and thus bring the trouble to an end. Therefore the following are suggested 
and recommended as probably the best methods of accomplishing this result: 

(1) Determine the location and extent of areas in which trees were attacked during the 
summer and fall (of 1901) and the number of trees now infested with living broods of the 
pine-destroying beetle. 

(2) Select those areas in which there are the largest number of infested trees and mark 
the same for cutting. 

(3) Secure, by sale contracts or otherwise, the cutting of these trees and the removal of 
the bark from the infested parts of the main trunks and stumps prior to May 1 ( 1902). The 
drying of the removed infested bark and surface of the wood will effectually destroy the 
insects. In addition the logs so treated will be protected next spring and summer from the 
attack of wood-boring insects, and thus be almost or quite as valuable for all commercial 
purposes as if cut from living trees. 

It is not necessary that all infested trees in the reserve or those of all other infested areas 
should be thus cut and barked, but it is important that a large percentage should be so 
treated in order to insure a sufficient reduction of the beetles to check their destructive 
ravages. 

Experience has shown quite conclusively that the above recom- 
mendations are entirely practicable, and it has also been demon- 
strated that whenever the felled trees are accessible for lumber, ties, 
mining timbers, or cord wood it can usually be sold for more than the 
cost of cutting and barking. 

APPLICATION OF THE METHOD IN THE BLACK HILLS. 

There has been a continued effort to control this destructive beetle 
in the Black Hills Reserve since 1901, but the adoption of the neces- 
sary radical measures was prevented by certain regulations governing 
the management of the reserve, which required the advertising and 
sale of the old dead and dying timber, for which there was not a suffi- 
cient demand in the State of South Dakota; and since a special pro- 
vision of the law prohibited the shipment of timber out of the State, 
it was practically impossible to accomplish anything of importance. 

We are informed, however, that the evident benefit in certain sec- 
tions resulting from cutting and barking the infested timber is such 
as to indicate that if more radical measures had been adopted under a 
more liberal policy of timber sales, and under a temporary amend- 



20 THE BLACK HILLS BEETLE. 

merit of the laws relating to its shipment out of the State, the 
destructive beetle could have been brought under complete control 
and millions of feet of valuable timber saved without cost to the 
Government. 

APPLICATION OF THE METHOD IN COLORADO. 

Pursuant to our recommendations, a large number of trees were 
felled during the past summer (1905) on private lands in and around 
Palmer Lake, Colorado, where between 500 and 1,000 trees had been 
killed within recent years over a comparatively small area. Observa- 
tions by the writer in October, and explorations by Ranger Edmon- 
ston in that vicinity, indicated a very slight new infestation this year. 
It is evident, therefore, that the efforts of the town board and of the 
citizens in cutting and barking the infested trees has had the desired 
effect in partially, if not completely, checking the destructive work of 
the beetle. If this good work is supplemented with a like effort on 
the part of forest officials during the coming winter, there is every 
reason to believe that the trouble in this vicinity will be brought under 
complete control, and that with a little well-directed effort each suc- 
ceeding year it can be kept within normal bounds. 

The same method was adopted by General Palmer and others,under 
the direction of Professor Bruner, in the vicinity of Colorado Springs 
and the Colorado pinery on the Platte and Arkansas Divide. The 
operation of barking and felling the affected dead and dying trees 
extended over an area of probably 150,000 acres, and between 600 and 
800 trees were felled and barked, and the bark burned with the tops. 

A thorough examination of this area by the writer indicates quite 
conclusively that the forces of the enemy have thus been sufficiently 
weakened to make their complete subjugation a comparatively easy 
matter, especially if the principal areas of present infestation in the 
reserve receive the proper treatment between now and the first of 
May. 

It is evident to the writer that in both localities considerable unnec- 
essary expense was involved in the cutting of old dead trees from 
which the enemy may have escaped and of those which might have 
recovered, as well as in burning the bark and tops, peeling the stumps, 
etc.; but it is plain that the losses from such unnecessary expen- 
ditures are of little consequence as compared with the great good 
accomplished. 



THE KLACK HILLS BEETLE. 21 

FURTHER RECOMMENDATIONS RELATING TO THE CONTROL OF 

THE BEETLE. 

(1) Explorations should be made, preferably during August, Sep- 
tember, and October, to locate the principal areas of new infestation. 

(2) Mark for cutting all clumps or patches of infested trees and 
some of the more accessible scattering ones in the worst-infested 
sections. 

(3) The best time to fell and bark infested trees is between the 
middle of October and the first of May. 

(4) If there is no demand for the timber, and more can be accom- 
plished by piling the trunks and tops and burning them, or sufficiently 
scorching the bark to kill the insects, this method may be followed; 
but barking the infested portion of the trunks, without burning the 
bark or tops, is preferable, since it will avoid the destruction of many 
beneficial insects, and the exposed broods of the destructive beetle 
furnish food for birds. 

(5) In some localities, and under certain conditions, it may be 
advisable to burn the tops, but if this is done to kill the insects it 
should be delayed until after the first of May and completed before 
the middle of June. ' 

(6) If for any reason the work of felling and barking the trees can 
not be undertaken or completed before the first of May, it may be done 
during May and June. The necessity for burning the bark and tops 
at such time will depend upon local conditions and requirements. 

(7) Summer operations should be avoided. There is nothing to be 
gained in felling freshly attacked trees which can just as well be cut in 
the fall and winter. In addition, there is danger of the freshly felled 
and barked trees exerting 'an attractive influence on the swarms of 
beetles which will cause them to attack the surrounding living timber. 
Then, again, any burning operations during the summer involves the 
danger of starting forest fires. 

(8) If it is especially desirable, on account of timber sale and 
logging contracts, to cut the old dead as well as the newly infested 
living trees during the active period of the insect — May to October — 
a thorough exploration should be made by a forest entomologist or a 
trained forester, who should be responsible for the marking of the 
infested living trees. It is also important that all cutting of infested 
timber be concentrated in the worst affected localities. 

(9) The burning of summer slash and the barking of stumps of 
trees which are healthy when felled is not necessary as a preventive 
measure against the Black Hills beetle, and the necessity for doing so 
against any other insect depends entirely on the species involved and 
local conditions. 



22 THE BLACK HILLS BEETLE. 

(10) The result of experiments and observations indicate that the 
trap-tree method can not be successfully adopted for this insect. 

(11) If a large amount of pine timber is blown down at any time, 
but especially in June and July, it should be carefully watched during 
the first year or two to determine whether or not it is attacked by the 
Black Hills beetle, and, if so, the bark should be removed during the 
fall after the attack is made. 

NOTE. 

The statements in this bulletin under the headings of "Life His- 
tory," "Natural and Artificial Influences," and "Methods of Con- 
trol" relate to the Black Hills beetle alone and are not applicable to 
any other species of barkbeetle. 



INDEX. 

Page. 

Adult, character 11 

Attack, influences aiding or inducing 16 

Birds as natural enemies 18 

Cold, as affecting infestation . 16 

Colorado Dendroctonus, distinguishing characters 11 

Control, in Black Hills 19-20 

in Colorado 20 

methods 19, 21 

Damage, extent 5 

Dendroctonus approximatus, distinguishing characters 11 

Colorado. See Dendroctonus approximatus. 
Douglas spruce. See Dendroctonus pseudotsugse. 

monticola, distinguishing characters 11 

piceaperda, distinguishing characters 11 

work in dead Engelmann spruce 10 

ponderosse — subject of this bulletin. 

pseudotsugse, distinguishing characters 11 

in western larch 11 

w< irk in dead Douglas spruce 10 

rujipennis, wrong determination 6 

terebrans, wrong determination 6 

valens, attacking fire-scorched trees 17 

distinguishing characters 11 

Destructiveness 5 

Development, time required 16 

Diseases 18 

Distribution 5 

Douglas spruce, attacked by Dendroctonus pseudotsugse 10 

Dendroctonus. See Dendroctonus pseudotsugse. 

Drought, as affecting infestation 16 

Eggs, time of depositing 15 

Enemies, insect 18 

Fire, as affecting infestation 16 

Food plants 5 

Fungous diseases 18 

Gallery, character 11 

Infested trees, indications of attack 13 

Larch, western, attack of Dendroctonus pseudotsugse 11 

Larvae, diseases 18 

habits 15 

Life history 15 

23 



24 INDEX. T 

Page. 
Lightning, as cause of infestation 16 

Mountain-pine beetle. See Dendroctonus monticola. 

Natural enemies 18 

Neutral insects 18 

Oregon Tomicus. See Tomicus oregoni. 

Parasitic enemies 18 

Picea canadensis, attack of Dendroctonus ponderosse 5 

engelmanni, attack of Dendroctonus ponderosse 5 

Pine, bull. See Pinus ponderosa. 
limber. See Pinus Jlexilis. 
western yellow. See Pinus ponderosa. 

Pinus jlexilis, attack of Dendroctonus ponderosse 5 

ponderosa, attack of Dendroctonus ponderosse 5 

Pitch tubes 13 

Predaceous enemies 18 

Remedial measures. See Control. 

Secondary enemies of trees 18 

Spruce, Douglas, attack of Dendroctonus pseudotsugse 10 

Engelmann. See Picea engelmanni. 

attack of Dendroctonus piceaperda 10 

See also Picea engelmanni. 
white. See Picea canadensis. 
Spruce-destroying beetle. See Dendroctonus piceaperda. 

Storm-felled trees, inducing infestation 16 

Temperature, as affecting infestation 16 

Tomicus oregoni, attack on trap trees 18 

Oregon. See Tomicus oregoni. 

Trap trees - 7, 17 

Turpentine beetle, large red. See Dendroctonus valens. 



o 



LBFe'07 




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